Lifting magnet for handling cargos

ABSTRACT

A lifting magnet for handling cargoes which includes an elongated pole piece rotatably attached to a framework suspended from a suspension device such as the hook of a cargo crane. The elongated pole piece is rotatably mounted on the framework for being rotated in a plane relative thereto. Thus, when the elongated pole piece is positioned on a plurality of elongated cargos such as I-beams with the longitudinal axis of the pole piece crossing the longitudinal axes of the I-beams, it is possible to lift a plurality of I-beams at the same time. On the other hand, when the elongated pole piece is rotated and positioned on only one I-beam with the longitudinal axes thereof being aligned, it is possible to lift only the selected I-beam.

United States Patent Kashiwagi et al.

Apr. 4, 1972 [54] LIFTING MAGNET FOR HANDLING CARGOS PrimaryExaminer-Evon C. Blunk Assistant ExaminerJ. Kenneth Silverman [72]Inventors: Shlnlchl Kashlwagi, Takasago; Mono Anomey oblom Fisher &Spivak Amano; Koichi Nakasawa, both of Hlmejl, all of Japan 57 ABSTRACT[73] Assign: Nishishiba Electric -s Himeji A lifting magnet for handlingcargoes which includes an elon- JaPan gated pole piece rotatablyattached to a framework suspended [22] Filed: July 14, 1970 from asuspension device such as the hook of a cargo crane. The elongated polepiece is rotatably mounted on the PP 54,786 framework for being rotatedin a plane relative thereto. Thus, when the elongated pole piece ispositioned on a plurality of [52] U S Cl 294/65 5 elongated cargos suchas i-beams with the longitudinal axis of [51] 1". .Cl the p pieceCrossing the longitudinal axes of the beams it is possible to lift aplurality of l-beams at the same time. On [58] Field of Search..294/65.5 the other hand, when the elongated p piece is rotated andpositioned on only one l-beam with the longitudinal axes [56] Referencescued thereof being aligned, it is possible to lift only the selected 1-UNITED STATES PATENTS beam- 3,487,964 1/1970 Riley ..294/65.5 7 Claims,11 Drawing Figures l3; T. l

PATENTEU 4 I9 2 SHEET 1 BF 4 mvrzn'rons SHINICHI KASHIWAGI MORIO AMANOKOICHI NAKASAWA 06m, Fir/M a! 9mm ATTORN EYS PATENTEDAPR 4 I972 SHEET 0F4 FIG. 10

LIFTING MAGNET FOR HANDLING CARGOS BACKGROUND OF THE INVENTION Thepresent invention relates generally to magnetic lifting devices, andmore particularly to an electromagnetic lifting device for handlingcargos, and similar loads which are made of magnetic materials.

In the past, many types of magnetic lifting devices have been providedfor handling cargoes and similar loads, the best known of which commonlysuspend the lifting magnet from the hook, or load-engaging member, of acrane. These devices have had to be relied upon for the handling ofvarious cargos in the field and although they have generally beensuccessfully employed, they have not always proven to be entirelysatisfactory in certain operations. One of these operations involves thehandling of elongated cargos such as I-beams, rails for railways, ingotsand the like.

It is sometimes necessary to load a truck with many elongated cargos ofthe aforedescribed character at the same time.

Whenever the truck has been substantially fully loaded, however, suchthat the loading ability of the truck will permit only one or twoadditional elongated cargos to be loaded thereon,

for example, or that the removal of only one or two of these cargos isrequired, the magnet must be able to selectively lift the aforesaid onlyone or two cargos therefrom.

In the magnetic lifting devices heretofore available, a circular surfaceor circular pole face is generally provided for magnetically attractingthe cargos. It can be understood that such magnets can be employed tolift many cargos of the character described simultaneously, but theycannot selectively lift a defined one or two of such cargos from amongthe others. Therefore, when it is required to lift one or two selectedcargos from among the others, it has been necessary to prepare othertypes of magnets having substantially rectangular configurations, orsuch other shape which is specifically adapted for the elongated cargosto be selectively lifted.

Such changing of the magnets for selectively lifting cargos, however, isnot readily accomplished, of course, unless magnets havingconfigurations different from each other have been previously readiedfor use. It is therefore not only expensive to make such preparations ofthe various types of magnets, but also it is inconvenientbecause thechanging of the magnets in presently available lifting devices ismanually performed and is considered to be a difficult operation.

SUMMARY OF THE INVENTION It is therefore an object of the presentinvention to provide a magnetic lifting device for use in various cargooperations which does not require changing of the lifting magnet to suitthe particular cargo in order to selectively lift only one or two of thecargos from among a larger number thereof.

Another object of the present'invention is to provide a magnetic liftingdevice for handling cargos in which the magnet includes an elongatedpole piece rotatably attached toa lower surface of a framework that issuspended from the book of a cargo crane.

Still another object of this invention is to provide a magnetic liftingdevice for selectively handling cargos in which the angular dispositionof an elongated pole piece relative to a lower surface of a frameworksuspended from the hook of a cargo crane can be automatically ormanually varied by a suitable drive.

A still further object of this invention is to provide a magneticlifting device for handling cargos in which an elongated pole piece isrotatably attached to a lower surface of a framework and can be rotatedby either an electric control signal from the control station of a cargocrane or a similar signal from a switch box suspended from the liftingmagnetic device.

Briefly, in accordance with the teachings of the present invention,there is provided a framework which is adapted to be suspended from asuspension device of a cargo crane. At least one electromagnetic polemember is mounted on the lower surface of the framework such that thepole member includes an elongated effective pole face to which cargosare magnetically attracted and the pole member can be rotated in a planerelative to the lower surface of the framework. A drive mechanism on theframework is effective for rotating the pole member within a desiredangle in the predetermined plane relative to the framework.

BRIEF DESCRIPTION OF DRAWINGS Various other objects, as well asadditional features and advantages of the present invention will be morefully appreciated as the same becomes better understood from thefollowing detailed description when considered in conjunction with theaccompanying drawings, wherein like reference numerals designate like orcorresponding parts throughout the several views, in which:

FIG. 1 is a schematic view of a lifting magnet device constructed inaccordance with the teachings of the present invention and shown beingsuspended from a cargo crane;

FIG. 2 is a plan view of one embodiment of the lifting magnet device ofthe invention;

FIG. 3 is an elevational view, partly in section, of the lifting magnetdevice of FIG. 2;

FIG. 4 is a bottom view of one of the elongated pole pieces of theembodiment illustrated in FIGS. 2 and 3;

FIG. 5 is a schematic of a circuit for controlling the excitation of theenergizing coils of the lifting magnet device of this invention;

FIGS. 6a and 6b are simplified perspective views illustrating two kindsof cargo lifting operations;

FIG. 7 is a side elevation of another embodiment of this invention;

FIG. 8 is a bottom view of one of the elongated pole pieces of theembodiment shown in FIG. 7;

FIG. 9 is a side elevation of still another embodiment of the presentinvention; and,

FIG. 10 is a bottom view of the device shown in FIG. 9.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to thedrawings, and more particularly to FIG. 1 thereof, a traveling cranegenerally designated by the reference numeral 10 is disposed on rails 11and 12 for movement in a direction perpendicular to the surface of thedrawing paper, or parallel with the rails.

Conventionally, the traveling crane 10 includes a girder 13, a controlroom 14 integrally constructed with the girder, and a crab 15mounted onthe girder for movement in a direction perpendicular to the path ofmovement of the traveling crane itself.

The crab carries a drum 16 for winding a steel rope, or cable 17, tolift a hook member 18 secured thereto, an electric hoisting motor l9'fordriving the drum, an electromagnetic brake (not shown)'for clamping thehoisting motor to prevent free lowering of the cargo when the motor isat a standstill, a mechanical friction brake (not shown) arrangedbetween the shaft of the motor 19 and the shaft of the drum 16 forabsorbing the potential energy of the lowering load being applied by theweight of the cargo, and an electric traversing motor (also not shown)for driving the crab 15 along the girder 13.

Although it is not shown, a trolley wire is provided along one of therails 11 and 12 for supplying the crane 10 with electrical power througha suitable connecting device (not shown) which slidably contacts thetrolley wire, whereby electrical power may be taken into the crane asdesired. The electric power taken into the crane is distributed throughvarious controllers provided in the control room and control panelboards conventionally mounted on the girder 13 for the aforedescribedhoisting motor 19 and traversing motor, as well as for a traveling motor(not shown) mounted on the girder for driving the crane as desired.

A lifting magnet generally designated by the reference numeral is shownbeing suspended from the hook 18. To energize and control the magnet 20,there are mounted on the girder 13 a relatively constant voltage source63, such as either an electric motor-generator or a static converterunit including a thyristor invertor and a thyristor rectifier, and acontrol panel board 64.

When the voltage being supplied to the trolley is from an A.C. powersource, an A.C. induction motor may be employed as the driving motor ofthe motor-generator unit to drive a D.C. generator of the same. On theother hand, where the voltage for the trolley is supplied from a D.C.power source, a thyristor inverter is preferably employed to convertD.C. to A.C., then the A.C. voltage is rectified by the thyristorrectifier to energize the magnet. It will be readily understood that theconstant voltage source 63 may include any suitable voltage regulatingdevice for supplying a relatively constant output voltage to theenergization circuit of the lifting magnet 20. This provision insuresagainst any sudden decrease in the energization voltage level of themagnet due to voltage variations such as are likely to occur uponstarting of the motors of the crane, whereby the cargos attracted to themagnet can thus be effectively prevented from being inadvertentlydropped out of the magnet.

To conduct an exciting current to the lifting magnet 20, a flexiblecable conductor 65, one end of which is wound around a cable drum 66rotatably mounted on crab 15, is suspended from the crab to a cableconnector 67 which is supported on the hook 18. Another cable 68, havingone end electrically connected to the lower end of the cable 65 throughthe connector 67, is connected at its other end to a terminal box 69mounted on the lifting magnet.

Although now shown, the shaft of the cable drum 66 is mechanicallyconnected to that of the wire cable drum 16 through a gear train,whereby cables 65 and 68 can be rolled up and down in synchronizedrelation with the hoisting and lowering activities of the hook 18.

The output of the control panel 64 is connected to a subtrolley wire 70extending along the girder and the end of the cable conductor 65 woundaround the cable drum 66 is slidably connected to the sub-trolley wirethrough a collector 71. The amplitude of the exciting current for themagnet 20 may be regulated by a regulating, or controller device 72,provided in the control room 14. A further function of this controller72 will be described hereinafter.

Referring now to FIGS. 2 and 3 for an explanation of the structuraldetail of the lifting magnet 20, there is shown a framework 21 whichacts as a yoke through which magnetic fluxes may be passed. Theframework, or yoke, is preferably made of cast steel and is formed in agenerally flat configuration. A pair of cylindrical pole members 22 and23 are integrally formed with the yoke member 21 and project downwardlyfrom the lower surface thereof adjacent opposite ends along a lengthwisedirection.

A main exciting coil 24 is concentrically wound around the cylindricalpole member 22, as shown in FIG. 3, and similarly, although notillustrated, another main exciting coil is concentrically wound aroundthe cylindrical pole member 23.

Elongated pole members 25 and 26 are provided below the lower ends ofcylindrical pole members 22 and 23 such that the longitudinal axes ofthe former are respectively positioned perpendicularly to the axes ofthe latter.

As is clearly shown in FIG. 2, the elongated pole members 25 and 26respectively include three elongated cast steel' blocks 27, 28, 29 and30, 31, 32 disposed in parallel, in which the centered blocks 27 andeach are of a length longer than those of the other two blocks disposedon either side thereof for the reason described hereinbelow. Also, bothelongated pole members 25 and 26 have a length such that one of the endsthereof protrudes beyond the opposite edge portions 33 and 34 of theyoke 21 to indicate their angular positions relative to the yoke,.

The three parts or blocks of each pole member are integrally assembledwith each other by any suitable fixture means such as welding, and eachpair of blocks disposed on opposite sides of the centered block have avertical dimension which is less than that of the centered block, one ofthe same 31 being shown in FIG. 3. Furthermore, the lower surface ofeach of such pairs of blocks are positioned slightly higher than thelower surface of the centered block as also shown by the relativepositioning of blocks 30 and 31 in FIG. 3. The purpose of thisarrangement will be set forth hereinafter. The amplitude of the totalwidth of elongated pole pieces 25 and 26 is chosen substantially equalto that of corresponding cylindrical poles 22 and 23.

In FIG. 4, there is shown a bottom view of theelongated pole piece 25.Of course, because the other piece 26 also has the same construction asthe piece 25, the explanation with a view thereof is omitted.

The centrally disposed block 27 has a rectangular slot 35 provided inthe bottom surface thereof along and near the four edges of the same. Asis shown in FIG. 3, there is embedded in this slot a formed coil 36 forthe purpose of exciting the centered block. The opening of the slotreceiving the exciting coil is then closed with wedges 37 inserted inthe slot, whereby the formed coil is prevented from dropping out.

Because the elongated pole members 25 and 26 are assembled on the yokemember in the same manner, respectively, only the method for assemblingthe elongated pole member 25 is disclosed in the drawing.

Thus, to assemble an elongated pole piece 25 with yoke member 21, thereis provided an opening 38 vertically extending through the cylindricalpole member 22. A tubular member 39 with a flanged portion 40 at oneend, preferably made of steel, is fixed to the centered area of theupper surface of the elongated pole piece 25 at the flanged portion 40.

Referring again to FIG. 4, there are provided a plurality of openings inthe elongated pole piece 25, which openings extend therethrough from thebottom surface of the pole piece to the upper surface of the same andrespectively receive therein a screw bolt 42. Thus, the threaded end ofeach bolt 42 is screwed into the flanged portion 40 of tubular member 39to secure the elongated pole piece to the tubular member. Of course, theelongated pole piece can be fixed to the tubular member, by othersuitable attachment methods, such as, for example, by welding.

A tubular portion 43 of tubular member 39 extends upward from thesecured flange portion 40 through the opening 38 in the cylindrical polemember 22, and then further extends through an aligned opening 44 in aring-shaped thrust collar 45, whereby the tubular member 39 is fixed atthe tubular portion 43 thereof with the collar 45 by any suitableaffixing means, such as bolts 46 extending through radial openings 47through the wall of the collar.

Around the opening 38 in yoke member 21 and on an upper surface of thesame is a thrust bearing seat 48 welded thereto to support the thrustforce resulting from the weight of the elongated pole assembly, wherebythe elongated pole piece 25 can be rotatably supported from the yokemember.

To rotate the elongated pole piece 25 around the central axis of tubularmember 39, an operational arm 49 is securely mounted on collar member 45by means of bolts 50, shown in FIG. 2, such that the arm is disposed onthe ring-shaped collar along a diameter thereof and the opposite ends ofthe arm extend over the peripheral portion of the collar.

To cause the exciting current to flow through the coil 36 embedded inthe slot 35 of the elongated pole piece, a cable conductor 51 isintroduced into a terminal of the coil through an opening 52 in the arm49 and an axially disposed cylindrical opening located within thetubular member 39 which is aligned therewith permitting the same to beconnected to the coil terminal.

Similarly, an operational arm 53 is securely mounted on a collar member54 connected to the elongated pole member 26 for causing it to rotate.

A pair of arms 49 and 53 are thereby located in parallel, as shown, andtheir corresponding ends are respectively connected with each other byelongate rods 55 and 56 having the same length. Thus, because the pairof arms 49 and 53 and the pair of rods 55 and 56 form a so-calledfour-link rocking mechanism, it is possible to rotate the pair ofelongated pole pieces 25 and 26 in desired parallel relation at alltimes.

To rotate the pair of elongated pole members 25 and 26 around thecentral axes thereof, an electric motor-driven fluid actuator 57 ispivotally mounted on the upper surface of yoke member 21 by means of apin member 60. The fluid actuator is a conventional oil pressure typeactuator and includes a piston with a piston rod (not shown)reciprocally located in a cylinder 58, which, in turn, is filled with anoil. The cylinder has an impeller (not shown) to be driven by anelectric motor 59 located at one end thereof. When the motor is rotatedin one direction, the impeller generates an oil pressure which functionswith the piston such that the same will be moved in one direction. Onthe other hand, where the motor drives the impeller in the reversedirection, the same will cause the piston to move in the reversedirection.

As is clearly shown in FIG. 3, the leftward end of the piston rodextends through the leftward end wall of the cylinder 58, where itrotatably engages a downward extension of a pin 61 mounted through oneend of the arm 49 through a connection rod 62.

Thus, when the motor 59 is rotated forward, the piston rod of theactuator is pushed out from the cylinder thereof, rotating the arm 49 ina counterclockwise direction (see FIG. 2). The rotation of the arm 49 istransferred through the rods 55 and 56 to the arm 53 to rotate it in thesame direction by the same angle as the aforesaid arm 49.

Such synchronized movements of the pair of arms are transferred to thepair of elongated pole pieces 25 and 26 through the tubular members 39being connected between thearms and the pole pieces, respectively. InFIG. 3, only one of the tubular members 39 connected between arm 49 andpole piece 25 is shown, but the other arm 53 and pole piece 26 are alsoconnected by a tubular member similar to the member 39.

It will be therefore readily understood that the pair of elongated polepieces 25 and 26 synchronously rotate in a counterclockwise directionduring forward rotation of the motor 59.

On the contrary, when the motor 59 is rotated in a reverse direction,the aforesaid movement of the parts will occur in a reverse direction,whereby the pair of pole pieces 26 and 26 will rotate in a clockwisedirection as seen in FIG. 2.

In FIG. 5, there is shown a typical excitation circuit for the maincoils 24 and 124, respectively, wound about cylindrical pole members 22and 23, as well as for coils 36 and 136 wound in slots 35 of elongatedpole members 25 and 26 as shown in FIG. 3.

One end terminal of each of the coils 24, 124, 36 and 136 is connectedtogether and then connected to a negative conductor, which, in turn, isconnected through the terminal box 69 to a lead of the cable conductor68 as shown in FIG. 1. The other terminals of coils 36 and 136 areconnected together at one point, and then connected through the terminalbox 69 to a positive lead of cable conductor 68. The other terminals ofmain coils 24 and 124 are also finally connected to the positive leadthrough the terminal box 69. However, this connection is made throughnormally open serially connected switches 73 and 74.

The switch contact 73 closes when the hoisting operation begins and thecontact 74 closes when a predetermined time interval elapses after thebeginning of the hoisting operation. The contact 74 belongs to a timingrelay 75 which functions when an electric signal corresponding to thebeginning of the hoisting operation is received by the relay from thecontroller 72 through a conductor 76 connected to the control panelboard 64. The series circuit including contacts 73 and 74 connected isemployed for selectively lifting cargos as described hereinafter.

To simultaneously excite all the coils, there is provided a normallyopen contact 77 connected across the series connected contacts 73 and74. This contact is closed when it is required that many cargos arelifted up at the same time as described hereinafter.

These contacts 73, 74 and 77 and the timing relay 75 are mounted in thecontrol panel board 64 and are controlled by the controller 72 locatedin the control room 14, as shown in FIG. 1

As is shown in FIGS. 2 and 3, the lifting magnet 20 is suspended fromthe hook 18 by means of four eye-bolts 78 secured onto the four cornerportions of the surface of the yoke member 21.

In operation, let us assume that it is necessary to lift a plurality ofcargos, such as I-beams 79 shown in FIGS. 6a and 6b, at the sametime..This operation is readily performed by positioning the pair ofelongate magnets 25 and 26 on the beams such that the longitudinal axesof the magnets are disposed perpendicular to those of the l-beams asshown in FIG. 6a. This is made by rotating the elongate magnets from thepositions shown in FIG. 2 to angular positions perpendicular thereto.The control of the rotation for the elongate magnets is maintained bythe electric motor driven oil pressure actuator 57 to which the controlsignal is given from the controller 72 in the control room 14 throughthe control panel board 64.

In this case, the contact 77 is closed, whereby all of the coils 24,124, 36 and 136 are fully excited at the same time. The lifting magnet20 will therefore generate a full rated output to magnetically attractmany of the cargos.

The magnetic fluxes induced by each pair of coils 24 and 36, as well ascoils 124 and 136, are respectively added to each other in therespective pole members, and the fluxes, for example, flow out from thepole face of one of the poles 25, then through the cargos made ofmagnetic material, flowing into the other pole 26, and then through theyoke member 21 so as to return back to the aforesaid pole 25.

The cargo handling operation as mentioned above is employed with theusual loading of cargos on a truck or a ship and is further employed tochange the cargos from one place to the other in which the same'are tobe loaded.

For example, upon the loading of a truck, assume that only a littlespace remains for loading only one or two l-beams thereon.

The pair of elongate magnets 25 and 26 are rotated to the position shownin FIGS. 2 and 6 by the oil pressure actuator 57 which may be driven bythe electric driving motor 59 thereof under the control of thecontroller 72 through the control panel board 64. The angular positionsof the pair of magnets 25 and 26 can be visibly established since oneend of each extends over the edge portion of the yoke member 21 and maybe observed from the operation room 14 of the cargo crane.

Such rotative motion of the elongate magnets 25 and 26 can also beinitiated by a manually operable switch such as a pendant typereversible switch 80 suspended from the terminal box 69 of the liftingmagnet 20.

Assume now that the pair of elongate magnets 25 and 26 have beenpositioned on an I-beam 79 such that their longitudinal axes are alignedwith each other along the longitudinal axis of a beam, as shown in FIG.6b.

When the hoisting control order is emanated from the controller 72, onlythe pair of coils 36 and 136 of the elongated magnets are at firstenergized from the control panel, starting the hoisting operation of thebeam and the contact 73 will close responsive to the hoisting operation,as will be understood from the circuitry illustrated in FIG. 5.

After a predetermined time delay following the initiation of thehoisting of the beam, the relay 75 is operative to close the contact 74thereof, whereby the pair of main coils 24 and 124 are energized suchthat the magnetic fluxes emanated therefrom are added to those of thecorresponding elongated coils to increase the magnetically attractiveforces to be generated by the latter.

Thus, it may be readily understood that prevention of drop out of theI-beam from the lifting device during the lifting operation may beachieved with the present invention. In this way, also, a single I-beamcan be handled in loading the same on the truck.

It can be, however, easily understood that by rotating the pair ofelongate magnets by any other angle in a plane, it is possible to liftany desired number of beams less than the maximum number capable ofbeing lifted.

As shown in FIGS. 2 and 3, each of the elongated pole members and 26includes a centered part 27 and 30 and a pair of side parts 28, 29 and31, 32, located respectively along opposite side walls of the centeredparts. The lower surfaces of the aforesaid side parts are in a slightlyhigher level than those of the centered parts. This insures that whenonly the coils 36 and 136 of the elongated pole pieces are excited forlifting only a single .l-beam, the clearance provided between theaforesaid lower surfaces of the side parts and the upper surface of thecargo provides a relatively high magnetic reluctance for the magneticfluxes which may flow therethrough, whereby it is possible to selectonly one l-beam to be lifted.

In another embodiment illustrated in FIG. 7, the lifting magnet 20includes a pair of elongated pole members 25 and 26 mounted on a yokemember 21 such that they can rotate around the central axes thereof. Therotation of the pole members are provided by electric motors 81 and 82which, in turn, provide reversible torques for the elongated polemembers through worms 83 and 84 secured to one end of the shafts of themotors and section gears 85 and 86 mounted partially around theperipheral portions of collar members 45 and 54. The collar members havea construction similar to those of FIGS. 2 and 3, except for theprovision in this embodiment of the sector gears being mounted on thesame.

Further, the lifting magnet disclosed herein does not include main coilsas shown in FIGS. 2 and 3. This serves to handle cargos which arerelatively light in weight compared with those being lifted with thedevice described in FIGS. 2 and 3.

FIG. 8 shows an enlarged bottom view of one of the elongated poles ofthe embodiment illustrated in FIG. 7. The elongated pole member 25includes a centered part made of cast steel having slots 87 and 88adjacent to longitudinally opposite ends thereof for receiving two coilsides ofa formed coil. The other two coil sides are mounted along theother opposite side walls in a lengthwise direction of the centeredpart, and are covered by elongated side parts 89 and 90 made of caststeel to protect the same. The openings of the slots and the openings ofthe side slots constructed between the centered part and the side coverparts are covered by wedges 100 inserted therein. The two side parts areintegrally secured with the centered part by employing any suitablemeans such as welding and bolting. The elongated pole member 25 issecured by welding to a lower surface of a cylindrical support 101 madeof cast steel and the same serves not only to support the pole member onthe yoke member, but also magnetically connects both members.

In accordance with this embodiment, the exciting coils can be easilymounted on the elongated pole members without specially machining thesame along their lengthwise directions to provide the slots forreceiving the elongate coil sides.

Also, because the rotation of the pair of elongated pole members isseparately controlled by the separated electric motors 81 and 82, thecomplicated mechanical interconnection which usually is required betweenthe pole members can be eliminated, and the entire driving mechanism forthe pole members thus becomes more simple and less expensive. At thesame time, however, the angular positions of the pole members can stillbe easily observed and controlled either in the control room of thecrane or from a place on the earth.

A further embodiment of the invention is shown in FIGS. 9 and 10, inwhich a substantially single elongated pole member 125 is provided. Thepole member 125 includes a centered part 102 and a pair of side parts103 and 104 located along the lengthwise-extending side walls of thecentered part, and these three parts are made of cast steel or thicksteel sheets, respectivel As best shown in FIG. 9, the centered part 102is provided with an integral cylindrical support member 105 on the uppersurface thereof substantially intermediate its ends such that the sameextends upwards from the centered part. The cylindrical support extendsthrough an opening 106 of a supporting frame 107 and the top portionthereof fits into an opening 108 of a collar member 109 and is securedthereto by means of screw rod members 110. A plurality of thrust balls111 are positioned between the bottom surface of the collar 109 and theupper surface of the frame 107 in corresponding ring-like groovesrespectively provided in the aforesaid surfaces.

An electric motor 112 is mounted on the frame 107 and by causing a worm113 thereof to engage with a sector gear 114 secured around the sidewall of the collar member 109, rotating the motor makes possible therotation of the elongated pole member 125 such that the same will assumea desired angular position in a horizontal plane.

Referring to FIG. 10 in which the bottom view of FIG. 9 is shown, thereare shown a plurality of coils 115 to posi tioned in spaced-apartrelation along a lengthwise direction of the elongated pole member 125.Each coil side of the coils is placed in a respective slot to 141 whichis machined in a direction perpendicular to the lengthwise of the polemember. The respective other two coil sides of each of the coils arepositioned along the longitudinal side walls of the centered part 102,and are respectively covered by side parts 103 and 104 to protect thecoil sides from, among other things, objects which may hit the coilsides. In the drawing, for the convenience of easily viewing the coils,the wedges generally inserted for retaining the coils have been removed.

There are provided magnetic poles 142 and 149 in areas surrounded bycoils such that they alternatively show north pole and south pole. It istherefore understood that magnetic fluxes emanated from one pole surfaceenter into the cargo made of magnetic material, flow therethrough, enterinto the adjacent pole via the surface thereof, and after that flowthrough the back portion of the centered part into the originated pole.Thus, the centered part 102 serves as a yoke member having a pluralityof magnetic poles.

To prevent reducing the effective magnetic fluxes, the lower surfaces ofboth side parts 103 and 104 are positioned in a plane slightly higherthan the lower surface of the centered part. In this way, because thereare defined air gaps between the lower surfaces of both side parts andthe upper surface of cargo, the magnetic reluctance in the gaps isincreased.

The lifting magnet as shown in FIGS. 9 and 10 can be effectivelyemployed for handling cargos such as l-beams H-beams and the like, whichhave a relatively short length.

Obviously, many modifications and variations of the present inventionare possible in light of the teachings of the present invention.Accordingly, although the invention has been explained by way of examplefor handling I-beams, l-I-beams and the like, it should be apparent thatthe invention can be readily adapted for handling other things such asscrap iron, ingots, billets, sheet bars, wires and rods. Additionally,the invention can be also adapted for an operation such as turning overthe sheet bar. It is therefore to be understood that within the scope ofthe teachings herein and the appended claims, the invention may bepracticed otherwise than as specifically described herein.

1. A lifting magnet for handling cargos comprising:

a frame member suspended from a crane being made of magnetic materialand serving as a magnetic yoke through which magnetic fluxes arepermitted to flow,

a pair of elongated magnetic pole members rotatably mounted on saidframe member for being rotated in a plane relative to the frame memberand being disposed thereon with the functioning surfaces thereofdirected toward cargos to be lifted thereby.

What is claimed and desired to be secured by Letters Patent I a firstexciting coil means respectively wound on each of said elongated polemembers,

a second exciting coil means mounted on said frame member for increasingthe magnetic flux being emanated from said first coil means when used incombination therewith,

control means connected to feed exciting currents to said first andsecond exciting coil means, and

rotating means mounted on said frame member to cause said elongatedmagnetic pole members to rotate in said plane.

whereby when said pair of elongated pole members are positioned on aselected elongated cargo such that the lengthwise axes of the pair ofpole members are aligned with the lengthwise direction of the cargo anda lifting operation of the cargo is initiated, said control meansinitially energizes only said first exciting coil means andsubsequentlyenergizes said second exciting coil means so as to addmagnetic fluxes emanated therefrom to those of said first coil meansafter starting the lifting operation of the cargo.

2. A lifting magnet for handling cargos according to claim 1,

wherein said rotating means comprises:

a link mechanism connected between said pair of pole members forsimultaneously rotating the pole. members, and

a driving means mounted on said frame member to rotate said pair of polemembers through said link mechanism.

3. A lifting magnet for handling cargos according to claim 2,

wherein said driving means is an electric motor-driven oil pressureactuator.

4. A lifting magnet for handling cargos according to claim 1,

wherein said control means includes means responsive to the start of thecargo lifting operation and a timing relay means operable after apredetermined interval of time elapses following the start of saidlifting operation,

whereby said second exciting coil means is energized through thecooperation of said operation starting responsive means and said timingrelay means for energizing said second exciting coil said predeterminedinterval of time after energizing said first exciting coil. 5. A liftingmagnet for handling cargos comprising: a frame member which is suspendedfrom a crane, at least one elongated magnetic member rotatably mountedon said frame member for being rotated in a plane relative to the framemember and being disposed thereon with the functioning surface thereofdirected toward cargos to be lifted thereby, and rotating means mountedon said frame member to cause said at least one elongated magneticmember to rotate in said plane, said at least one elongated magneticmember being in three parts respectively made of magnetic materialincluding an elongated center part and side parts located alonglengthwise opposite side walls of the center part, said center partincluding a plurality of slots located perpendicularly to saidlengthwise direction and being spaced apart for receiving two oppositecoil sides of an exciting coil therein, the other two opposite coilsides of said exciting coil being located along the lengthwise oppositewalls of said center part, and said side parts respectively coveringsaid other two opposite coil sides for protecting the same. 6. A liftingmagnet for handling cargos according to claim 5, wherein Y the lowersurfaces of said two side parts of said at least one elongated magneticmember facing said cargos is disposed at a higher level relative to saidcargo than the corresponding lower surface of said center part. 7. Alifting magnet for handling cargos according to claim 1, wherein atleast one end of each of said elongated magnetic pole members extendsover the peripheral edge of said frame member to indicate the angularposition thereof when said magnetic pole members are rotated in a planerelative to said frame member.

1. A lifting magnet for handling cargos comprising: a frame membersuspended from a crane being made of magnetic material and serving as amagnetic yoke through which magnetic fluxes are permitted to flow, apair of elongated magnetic pole members rotatably mounted on said framemember for being rotated in a plane relative to the frame member andbeing disposed thereon with the functioning surfaces thereof directedtoward cargos to be lifted thereby. a first exciting coil meansrespectively wound on each of said elongated pole members, a secondexciting coil means mounted on said frame member for increasing themagnetic flux being emanated from said first coil means when used incombination therewith, control means connected to feed exciting currentsto said first and second exciting coil means, and rotating means mountedon said frame member to cause said elongated magnetic pole members torotate in said plane. whereby when said pair of elongated pole membersare positioned on a selected elongated cargo such that the lengthwiseaxes of the pair of pole members are aligned with the lengthwisedirection of the cargo and a lifting operation of the cargo isinitiated, said control means initially energizes only said firstexciting coil means and subsequently energizes said second exciting coilmeans so as to add magnetic fluxes emanated therefrom to those of saidfirst coil means after starting the lifting operation of the cargo.
 2. Alifting magnet for handling cargos according to claim 1, wherein saidrotating means comprises: a link mechanism connected between said pairof pole members for simultaneously rotating the pole members, and adriving means mounted on said frame member to rotate said pair of polemembers through said link mechanism.
 3. A lifting magnet for handlingcargos according to claim 2, wherein said driving means is an electricmotor-driven oil pressure actuator.
 4. A lifting magnet for handlingcargos according to claim 1, wherein said control means includes meansresponsive to the start of the cargo lifting operation and a timingrelay means operable after a predetermined interval of time elapsesfollowing the start of said lifting operation, whereby said secondexciting coil means is energized through the cooperation of saidoperation starting responsive means and said timing relay means forenergizing said second exciting coil said predetermined interval of timeafter energizing said first exciting coil.
 5. A lifting magnet forhandling cargos comprisiNg: a frame member which is suspended from acrane, at least one elongated magnetic member rotatably mounted on saidframe member for being rotated in a plane relative to the frame memberand being disposed thereon with the functioning surface thereof directedtoward cargos to be lifted thereby, and rotating means mounted on saidframe member to cause said at least one elongated magnetic member torotate in said plane, said at least one elongated magnetic member beingin three parts respectively made of magnetic material including anelongated center part and side parts located along lengthwise oppositeside walls of the center part, said center part including a plurality ofslots located perpendicularly to said lengthwise direction and beingspaced apart for receiving two opposite coil sides of an exciting coiltherein, the other two opposite coil sides of said exciting coil beinglocated along the lengthwise opposite walls of said center part, andsaid side parts respectively covering said other two opposite coil sidesfor protecting the same.
 6. A lifting magnet for handling cargosaccording to claim 5, wherein the lower surfaces of said two side partsof said at least one elongated magnetic member facing said cargos isdisposed at a higher level relative to said cargo than the correspondinglower surface of said center part.
 7. A lifting magnet for handlingcargos according to claim 1, wherein at least one end of each of saidelongated magnetic pole members extends over the peripheral edge of saidframe member to indicate the angular position thereof when said magneticpole members are rotated in a plane relative to said frame member.